fragment can not go back to previous state when press Back button
Question
Hi I have a app that follow as follow: MainActivity use navigationDrawer to navigate between fragment for example fragment1 , fragment2 , fragment3 . Fragment1 Contain tablayout fragment1-A and child fragment1-B and fragment1-C . when user in fragment1-B click a button, they will go to another fragment1-Ba (this transaction will be add to backstack). When user press backButton in fragment1-Ba . They will go back to fragment1-B by these code in the MainActivity .
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
// if got BackStack, come back to it
if (fragmentManager.getBackStackEntryCount()>0) {
super.onBackPressed();
// if not come to home screen
}else {
if (!homeFlag) {
fragment = new MainFragment();
fragmentManager.popBackStack();
fragmentManager.beginTransaction().replace(R.id.contentMainDrawer, fragment).commit();
homeFlag = true;
} else exit();
}
}
}
But when user inside fragment1-Ba (2nd tablayout fragment ) if they press BackButton . It give the error and crash the app (inside fragment1-Ba press backButton work normally)
this is the error. Anyhelp is much appreciate. Thanks.
12-31 12:20:22.118 9719-9719/victory1908.nlbstafflogin2 E/AndroidRuntime: FATAL EXCEPTION: main
Process: victory1908.nlbstafflogin2, PID: 9719
java.lang.IndexOutOfBoundsException: Invalid index 1, size is 0
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
at java.util.ArrayList.get(ArrayList.java:308)
at android.support.design.widget.TabLayout.getTabAt(TabLayout.java:448)
at android.support.design.widget.TabLayout$TabLayoutOnPageChangeListener.onPageSelected(TabLayout.java:1759)
at android.support.v4.view.ViewPager.dispatchOnPageSelected(ViewPager.java:1794)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:548)
at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:514)
at android.support.v4.view.ViewPager.onRestoreInstanceState(ViewPager.java:1320)
at android.view.View.dispatchRestoreInstanceState(View.java:14564)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3157)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3163)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3163)
at android.view.View.restoreHierarchyState(View.java:14542)
at android.support.v4.app.Fragment.restoreViewState(Fragment.java:468)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1094)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1248)
at android.support.v4.app.BackStackRecord.popFromBackStack(BackStackRecord.java:958)
at android.support.v4.app.FragmentManagerImpl.popBackStackState(FragmentManager.java:1666)
at android.support.v4.app.FragmentManagerImpl.popBackStackImmediate(FragmentManager.java:586)
at android.support.v4.app.FragmentActivity.onBackPressed(FragmentActivity.java:169)
at victory1908.nlbstafflogin2.MainActivity.onBackPressed(MainActivity.java:134)
at android.app.Activity.onKeyUp(Activity.java:2550)
at android.view.KeyEvent.dispatch(KeyEvent.java:3159)
at android.app.Activity.dispatchKeyEvent(Activity.java:2805)
at android.support.v7.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:50)
at android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.dispatchKeyEvent(AppCompatDelegateImplBase.java:224)
at android.support.v7.view.WindowCallbackWrapper.dispatchKeyEvent(WindowCallbackWrapper.java:50)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:2429)
at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:4508)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4463)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4020)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4073)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4039)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4153)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4047)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4210)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4020)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4073)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4039)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4047)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4020)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4073)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4039)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4186)
at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:4347)
at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2480)
at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:2074)
at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:2065)
at android.view.inputmetho
2 answers
solution1
0 2015-12-31 04:33:31
- Store fragment name is public static variable lastFragment...
- update it whenever moving to new fragment by setting its previous fragment ....
- make it null in main activity ... -exit app if it is null otherwise replace fragmentmanger with lastFragment.
solution2
0 2015-12-31 05:09:45
Ok. I got your problem. This is because getBackStackEntryCount() is returning Zero. So you need to add below lines after committing your fragment onBackPressed Button.
fragmentManager.executePendingTransactions();
and add
fragmentManager(null, FragmentManager.POP_BACK_STACK_INCLUSIVE) instead of fragmentManager.popBackStack();
FragmentManager.POP_BACK_STACK_INCLUSIVE ) is usedto pop the entire back stack.
See this discussion
Editing in your code :
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
// if got BackStack, come back to it
if (fragmentManager.getBackStackEntryCount()>0) {
super.onBackPressed();
// if not come to home screen
}else {
if (!homeFlag) {
fragment = new MainFragment();
fragmentManager(null, FragmentManager.POP_BACK_STACK_INCLUSIVE)// Change
fragmentManager.beginTransaction().replace(R.id.contentMainDrawer, fragment).commit();
fragmentManager.executePendingTransactions();// Change
homeFlag = true;
} else exit();
}
}
}
Hope it help you.
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